Update to /external/robolectric rather than older /external/robolectric-shadows am: 6d1129c791

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/services/Mms/+/21182126

Change-Id: Ia0f6dfc1d20435bba6e5e875ad92b428b15b835b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>